Torsional Vibrations Apparatus

Technical DescriptionThe model enables rotary vibration on torsion bars to be investigated. The model consists of a wall mounted base frame made of aluminum. The carrier plate has a strong chuck with the aid of which the torsion bars can be clamped in position. In the same way the mass disc and the mass ring are clamped to the torsion bar using a chuck. The effective length is easy to adjust.Theoretical BackgroundTorsional vibrationis angularvibrationof an object commonly a shaft along its axis of rotation.Torsional vibrationis often a concern in power transmission systems using rotating shafts or couplings where it can cause failures if not controlled. In ideal power generation, or transmission, systems using rotating parts, not only thetorquesapplied or reacted are "smooth" leading to constant speeds, but also the rotating plane where the power is generated (or input) and the plane it is taken out (output) are the same. In reality this is not the case. The torques generated may not be smooth (e.g.,internal combustion engines) or the component being driven may not react to the torque smoothly (e.g.,reciprocating compressors), and the power generating plane is normally at some distance to the power takeoff plane. Also, the components transmitting the torque can generate non-smooth or alternating torques (e.g., elastic drive belts, worn gears, misaligned shafts). Because no material can be infinitely stiff, these alternating torques applied at some distance on a shaft causes twisting vibration about the axis of rotation.The following formulas are used for torsional vibration and can be verified by experimentally.

Learning Objectives / Experiments- Experiment Setup:Objective: Determination of the period of torsional vibration as a function of:1. Torsionwire length2. Torsion wire diameter3. Rotating mass and its formProcedure1- Fix the bracket at convenient position along the beam2- Grip the shaft at bracket by means of chuck and tighten it tighten key3- Fix the rotor on the other end of shaft4- Note the length of shaft with a measuring tape5- Twist the rotor through some angle and release.6- Note down the time required for 50 oscillations with a stop watch7- Repeat the procedures for five times

Observation: Sr. No.Length of Shaft (m)Time taken for 50 oscillations (sec)Period of vibration ( Sec)

t1t2t3t4t5TexpTtheo

1

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5